The present invention relates to a method for starting an engine of a vehicle having a hybrid transmission and particularly to a technique for suppressing vibrations caused by torque variations at start of an engine. The present invention further relates to an apparatus for carrying out the method.
A hybrid transmission is capable of providing motor running in which a vehicle is driven by the power of an electric motor only and hybrid running in which the vehicle is driven by the power of both of an engine and the electric motor. The power of the engine is supplied to the hybrid transmission by way of a clutch.
In the vehicle with the hybrid transmission, motor running is used at start of the vehicle for the reason of smooth start and easy control.
In the meantime, when the vehicle speed exceeds beyond a certain value after start of the vehicle, it is usual practice to drive the vehicle by the power of the engine in place of or in combination with the power of the motor.
Accordingly, during motor running after start of the vehicle, the clutch between the hybrid transmission and the engine is engaged to crank the engine, and when the engine speed increases to startable speed, the engine is started by fueling and firing.
In the meantime, at start of the engine, the engine is unstable in operation, thus causing torque variations which are delivered to a vehicle wheel driveline to cause vibrations.
As a countermeasure for a shock at the time of changing of a running mode from the motor running to engine running in which the vehicle is driven by the power of the engine only, there is known such one as disclosed in Unexamined Japanese Patent Publication No. 11-082261.